1. Field of the Invention
The present invention relates to a motorized paper shredder. The present invention is based on Chinese Utility Model Application No. 201020543836.3, filed on Sep. 27, 2010, and Chinese Utility Model Application No. 201120246575.3, filed on Jul. 13, 2011. The contents of the above-mentioned applications are incorporated herein by reference.
2. Description of Related Art
A motor, also called electric motor, is an energy conversion or transfer electromagnetic apparatus that functions according to the law of electromagnetic. It's main use to generate drive torque, thereby becoming the appliance or a power source of the various mechanical. Because motor operation is developed by solenoid cutting action, and the current resistance of the effect must produce heat, the greater the current, the more heat it generates. In continuous operation, the motor will accumulate a large amount of heat affecting the overall performance of the motor, thereby reducing the efficiency of the motor operation, thereby increasing the running cost of the motor.
To solve the above problem, Chinese Utility Model No. 201290050, discloses a “motor heat dissipating device” on Aug. 12, 2009, it's technical features comprises a motor body, a housing for covering the motor body, a cooling water tank and a pump, said housing is equipped with a water outlet hole and a water inlet hole and with external piping, connects with the cooling water tank to form a circulating loop; the pump is installed in between the cooling water tank and the water inlet hole; the housing seals the motor body, and there is a water holding space in between the housing and the motor body; when the motor is in operation, the pump pumps water from the cooling water tank, and through the water inlet hole, pumps the water into the water holding space and by using the hydro-cooling method, cools the motor body; the water then flows, through the water outlet hole, back the cooling water tank to allow repeated use. The motor heat dissipating device of this invention adapts the hydro-cooling method, pumping cooling water from the cooling water tank to cool off the heat giving off from the motor, and via the cooling water tank to loop cooling water and heat exchange. This method can increase heat dissipation, enhance motor operation efficiency, and thereby reducing the running cost of the motor. However, the structure of this type of water-cooling heat dissipating device is more complicated and subject to set up additional external cooling water loop pipe, when used in combination with other mechanical components is not easy.
In addition, the rotor of the motor is provided with a number of coils, when the motor is operating, the coils give off the most heat, and then the coil of the stator of the motor give off the second most heat. The heat from the rotor may be conducted through air to the motor housing; there is a low thermal conductivity between the rotor and the motor housing, hence, thermal conduction is slow. Whereas, CN201290050 technical solution focuses on heat dissipation on the motor housing, the heat dissipation effect is limited
Chinese Patent Publication No. CN2751887Y discloses a heat dissipating device for paper shredder wherein, on one side of the motor a heat dissipating fan is installed and on the other side of the motor several heat dissipating holes are provided. The shortcoming of this invention is that the heat dissipating from the heat dissipating holes still remain in the paper shredder housing, and mixed with the heat dissipating from other components, affecting the cooling efficiency of the motor. Because heat dissipating fan is mounted on one side of the motor while the other side of the motor is mounted with an output shaft, no further fan can be mounted, because the high speed rotation of the output shaft can shake off a fan mounted on it, and to cause mechanical failure. This also constitute a constraint to designers on further increasing the cooling efficiency.
In another prior art, it provides a motor heat dissipating device having the structure: having heat dissipating holes directly on motor housing body. The motor heat dissipating device with this structure although may allow the heat from inside of the motor to dissipate from the dissipating holes, however, this type of heat dissipation is conducted by natural flow of air, hence heat dissipating efficiency is low, and heat is easily accumulated inside the motor. In another type of motor heat dissipating device, the heat dissipating device is arranged around the motor housing body, and allows close fit of the heat dissipating device and the motor housing body, with this structural characteristics, the heat dissipating area and efficiency are increased for the motor heat dissipating device, however, the device may be bulky, requires the motor to occupy more space.
There are other prior arts also provide a number of motor's cooling structures, but their structures are complex and assembly are not easy, and required higher manufacturing costs.
Therefore, with these deficiencies in the prior arts, there is a need to provide a paper shredder, where this paper shredder would have a heat dissipating device for the motor, with great cooling effect, can achieve rapid cooling of the motor, have a long continuous shredding time short motor recovering time long operating life simple structure easy assembly, and with characteristics to facilitate market-oriented promotion and application.